The goals of the research project are to develop and evaluate the possible use of electron radiography (ionography) for large population breast cancer screening with image resolution and breast cancer detectability equal to currently available techniques but with much lower dose per examination. The following characteristics of an electron radiographic mammography image chamber will be determined: 1. Resolution through measurement of its edge spread function (ESF) and line pair resolution of a gold test pattern. 2. Definition through measurement of receiver operating characteristic curves (ROC) and imaging of a modified Stanton mammography phantom. 3. Cancer detection through comparison with conventional techniques (film and xeroradiography) of electron mammographic radiographs of suspected neoplastic breast lesions. 4. Sensitivity through measurement using film and thermoluminescent dosimeters of the dose necessary to obtain optimally imaged abnormal breasts.